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Smaller Voles: “Evolution in Action” Is Rare, Trivial

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News from the University of Zurich is notable both for how underwhelming it is and for a “rare” admission. Researchers documented that as winter came earlier, snow voles got smaller. That seemed counterintuitive since, as the title of the publication in PLOS Biology asks rhetorically, “Bigger Is Fitter?”

Well, isn’t it? Not so in this case, apparently. Why?

In principle, larger snow voles are fitter: They have better capabilities to survive and reproduce. Despite this positive correlation at the phenotypic level, however, a converse causal relationship was evident on the genotypic level. “The voles whose genetic make-up led to a lower body weight were the fittest, especially in years when the first winter snow fell earlier than usual,” explains the biologist. This may be because lighter young are more likely to reach their final size before the weather deteriorates and winter comes.

Fine. Maybe so. But notice the welcome candor in announcing this result. Observing this cute mouse-like rodent getting a bit smaller seems to be pulled straight from the voluminous files of unimpressive evidence for Darwinian evolution’s grand claims. Evolution is supposed to explain how fantastic novelties arise, not merely why a little animal gets a bit smaller (or bigger). Even such an instance, though, they say repeatedly, is “extremely rare.”

Researchers from the University of Zurich have succeeded in documenting an extremely rare case of evolutionary adaptation “in action” among wild snow voles near Chur.

Although this process is well understood in breeding conditions and in the lab, it is still largely unclear how often and how rapidly it takes place under natural conditions. Examples of contemporary adaptive evolution remain extremely rare.

If the scientists had restricted their observations solely to phenotypic traits, such as body size and weight, this rare example of “evolution in action” in the wild would have remained hidden. [Emphasis added.]

And again, from the Abstract:

In natural populations, quantitative trait dynamics often do not appear to follow evolutionary predictions. Despite abundant examples of natural selection acting on heritable traits, conclusive evidence for contemporary adaptive evolution remains rare for wild vertebrate populations, and phenotypic stasis seems to be the norm.

So stasis is the “norm,” and seeing “evolution in action” in the wild is “extremely rare.” And where found, as it was here, one might add that it is pretty trivial. Perhaps they thought we weren’t listening.

Photo: Snow vole, by Timothée Bonnet via University of Zurich.

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